(I), which was prepared by Chichibabin as early as 190713. Schwab and Agliardi have observed that hydrocarbon I catalyzed the interconversion of ortho-and para-hydrogen; they have attributed this catalytic activity to the presence of the biradical structure (Ib) in the hydrocarbon23. On the other hand, Müller and Müller-Rodloff have assigned the quinomethane structure (Ia) on the basis of the diamagnetic behavior of this ...
